Magnetic actuator mechanism

ABSTRACT

A magnetic actuator comprising a stationary magnetic core structure having two distinct magnetic flux paths, with a movable armature included in both the flux paths and movable between a rest position and an actuated position. A permanent magnet or winding provides reset or restore flux, and a first winding includes the armature and opposes the restore flux. A second winding provides the major armature attractive force.

Umted States Patent 1 91 1111 3,745,495 Chai et al. 1 1 July 10, 1973 MAGNETIC ACTUATOR MECHANISM FOREGN PATENTS OR APPLICATIONS 1 lnvemorsi Hi Chai, Binghamton; Stephen 1,926,514 12/1969 Germany 335/229 H. Mills, Newark Valley; Joseph P. Pawletko; Francis E. Peters, f 0f Carl Young, Primary Examiner-George Harris Hillcrest, all of NY. Att0mey-Paul M. Brannen et al.

[73] Assignee: International Business Machines Corporation, Armonk', N.Y. 221 Filed: 066. 16, 1971 [57] ABSTRACT PP 208,569 A magnetic actuator comprising a stationary magnetic core structure having two distinct magnetic flux paths, 521 US. 01. 335/229 101/93 0 3 included flux 51 1 1m. (:1. "11011 7/08 and heme" a and an [58] Field 61 Search 335/229 230 236 med A Pe'mmm winding 7 335/274. 101/93 C R vides reset or restore flux, and a first winding includes the armature and opposes the restore flux. A second [56] References Cited winding provides the major armature attractive force.

UNITED STATES PATENTS 3,671,899 6/1972 c111: 335/214 x11 3 PAIENIEDJUHO'W I 3.745.495

INVENTORS HI D. CHAI STEPHEN H. MILLS JOSEPH F? PAWLETKO FRANCIS E. PETERS CARL T. YOUNG BY WZ AGENT 1 MAGNETIC ACTUATOR MECHANISM FIELD OF THE INVENTION This invention relates generally to electromagnetic actuator mechanisms and particularly to high-speed compact magnetic actuators for operating printing hammers, or matrix wires in wire matrix printers.

DESCRIPTION OF THE PRIOR ART Print hammer actuators previously have used springs or mechanically-operated restoring devices to reset the movable parts to this rest position. Such devices involve a number of moving parts and/or are bulky and less efficient than arrangements embodying the present invention.

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a new and novel electromagnetic actuator mechanism.

Another object is to provide an improved magnetic actuator having improved operating efficiency.

A further object of this invention is to provide an improved magnetic actuator mechanism having only one movable element, namely, the armature.

A still further object of the invention is to provide an electromagnetic actuator mechanism which is economical in volume occupied and in construction.

Yet another object of the present invention is to provide a magnetic actuator mechanism which utilizes a restoring magnetic field to restore the mechanism to its rest or reset condition, and wherein the restoring flux is negated when the actuator is driven to its operated condition.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a diagrammatic view showing, in schematic form, a side elevation of a magnetic actuator mechanism comprising a first embodiment of the invention;

FIG. 2 is a diagrammatic view, showing, in schematic form, a side elevation of a magnetic actuator mechanism comprising a second embodiment of the invention; and

FIG. 3 is a diagrammatic view, showing, in schematic form, a side elevation of a magnetic actuator mechanism comprising a third embodiment of the present invention.

Similar reference characters refer to similar parts in each of the several views.

DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 of the drawings shows schematically a magnetically-operated actuating device constituting a first embodiment of the present invention. In this embodiment, a magnetic core having three distinct legs connected by a common portion 3 is provided, the leg portions being designated by the reference characters 5, 7 and 9, respectively. A pole piece of magnetic material 11 is provided to complete one portion of the magnetic circuit, and the portion may be of any suitable permanent magnet material to provide a retaining or holding magnetic force, as will be subsequently described. The center leg of the stationary core structure 7, is surmounted by a pole piece 13, which has an opening therethrough to permit passage to and fro of an armature 15, also of magnetic material. The upper portion of the leg 9 is turned to provide an inwardlyprojecting portion which is in line with the armature 15. The upper portion of the leg 9 has an opening therethrough to receive an actuating rod 17, which is connected to the armature l5 and serves to transmit motion therefrom to whatever utilization device is to be operated by the actuator, for example, the print hammer of a printing mechanism. It may also be noted that the wire or rod 17 may be used directly as a printing element in a wire matrix type printer in which a plurality of selected wires are impacted against a paper and ribbon combination to provide a character impression.

Each of the three legs of the core structure has a source of magnetomotive force associated therewith. The leg 5 has a permanent magnet shown for a source of magnetomotive force, but it will be apparent that an electromagnetic source of flux could be used by providing an appropriate winding on portion 5.

An operating coil 19 is associated with leg 9 of the core, and a bucking coil 21 is associated with the portion 7 of the core. The armature 15 is guided for motion within the element 13, which therefore can serve not only as a channel or guide means for the armature 15, but also as a portion of the flux path.

The apparatus as shown in its normal condition in which the flux from the permanent magnet circulates through the core structure in the paths indicated by the dash lines with arrowheads. A portion of the flux from the permanent magnet 5 will pass down through the portion 7 of the core and the remainder circulates through the portion 9 of the core. This will cause the traction of the armature 15 to its normal or rest position in which it abuts the pole face 11 of the structure, as shown.

To operate the actuator mechanism, the coils l9 and 21 are appropriately energized so that coil 21 causes an opposing flux in the leg or portion 7 of the core, which opposes the flux emanating from the permanent magnet. This opposing flux will be at least sufficient to neutralize the permanent magnet flux which would otherwise circulate through the common leg. This forces the flux from the permanent magnet to travel the longer path through the portion 9 of the core, thereby reducing the attractive force between the pole piece 11 and the end of armature 15. At the same time, the magnetomotive force generated by the current in winding 19 is sufficient to overpower the flux from the permanent magnet, so that armature 15 is operated toward the right, until its right-hand end abuts the end of the leg 9 of the core.

When the current is removed from coils l9 and 21, the flux from the permanent magnet is again sufficient in strength to cause armature 15 to be attracted back to its normal rest position abutting pole face 11. The coil 21 can be driven either in parallel or series with coil 19, or driven independently. Also, since coil 21 is intended to speed up the start of motion of the armature, it may not be necessary to drive it for the same length of time as coil 19. Moreover, the actual time of operation for energization of the coils may differ since coil 21 could be energized before coil 19 and its energization terminated before coil 19 is de-energized.

The arrangement shown provides improved results by reducing of the time of operation and with the increased efficiency the heating due to the energization of the coils is reduced thereby allowing higher duty cycles. This configuration also lends itself to producing of relatively narrow magnetic structures which allows a construction in which a plurality of these devices may be assembled in a relatively small volume. An additional advantage is the fact that only a single moving element is involved to operate the wire or rod 17, namely, the armature 15, thereby reducing the service and repair requirements;

In FIG. 2 of the drawings there is shown a modification of the basic arrangement shown in FIG. 1 and described hereinbefore, in which a pivoted armature is employed and in which the armature itself forms a portion of the third leg of the magnetic circuit. It will be apparent that the relative relationship of the parts in the circuit are reversed or transposed from that shown in FIG. 1, but it will also be apparent that the various parts occupy the same relative relationships as they do in FIG. 1. In FIG.,2, the permanent magnet 5 is included in a magnetic path which includes a portion 3a of the bottom part of the core structure, and the pole piece 11. The armature 23 completes a magnetic circuit for this portion of the structure, the armature having a knife edge portion 25 which rests in a suitable V- groove in a notch in support 27 to permit the armature to rock or pivot in the plane of the drawing, from its normal resting position abutting the permanent magnet portion of the circuit to rotate toward the left thereby operating the print wire or rod 17. Operation of the actuator configuration shown in FIG. 2 is similar to that described above in FIG. 1 in that energization of coils l9 and 21 cause the flux from the permanent magnet to be bucked out or opposed in the middle portion of the armature, so that the flux from coil 19 is effective to rapidly attract the upper end of armature 23 to its left-hand or operated position. When the coils are deenergized, the permanent flux once again takes over and restores the armature to its right-hand or rest position.

FIG. 3 of the drawings shows a further modification of the previous two arrangements, in which an armature 23 is rotated about a pivot 31, and has a portion 33 projecting from the main body of the armature to abut the end of the portion 9 of the core 3b, when the armature is in its operated position. Operation of this arrangement is identical to that described above for FIG. 2, and hence, need not be further described.

The advantage of using the pivoted armatures is to provide another degree of freedom in the design of the mechanism, in that by shaping the armature body, the inertia and equivalent mass can be controlled while in the actuator having linear motion, shown in FIG. I, only the volume of the armature can be varied.

The pivoted or rotating version illustrated in FIGS. 2 and 3 are therefore more advantageous in low energy applications where the linear mass cannot be reduced below certain levels.

From the foregoing it will be apparent that the present invention provides a novel and improved configuration of magnetic circuit elements to provide a magnetic actuator having only a single moving part and lending itself to structures wherein high efficiencies and reduced heating can be obtained and because design characteristics can be encompassed in a small volume.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An electromagnetic actuator mechanism comprising, in combination,

an armature pivoted at one end for rotation about the pivot axis, between a reset position and an operated position,

a reset flux magnetic circuit including a permanent magnet and having a U-shaped configuration with the legs of the circuit being bridged by the armature when the armature is in its reset position,

an operating flux magnetic circuit including a source of operating flux and having a U-shaped configuration with the legs of the circuit being bridged by the armature when the armature is in its operated position, and

opposing flux means for generating opposing flux which opposes said reset flux during at least a portion of the time said operating flux is effective.

2. An electromagnetic actuator mechanism as claimed in claim 1, in which said reset flux circuit permanent magnet is disposed in the central portion of the reset magnetic circuit.

3. An electromagnetic actuator mechanism, as claimed in claim 1, in which said opposing flux means comprises a winding linking said armature. 

1. An electromagnetic actuator mechanism comprising, in combination, an armature pivoted at one end for rotation about the pivot axis, between a reset position and an operated position, a reset flux magnetic circuit including a permanent magnet and having a U-shaped configuration with the legs of the circuit being bridged by the armature when the armature is in its reset position, an operating flux magnetic circuit including a source of operating flux and having a U-shaped configuration with the legs of the circuit being bridged by the armature when the armature is in its operated position, and opposing flux means for generating opposing flux which opposes said reset flux during at least a portion of the time said operating flux is effective.
 2. An electromagnetic actuator mechanism as claimed in claim 1, in which said reset flux circuit permanent magnet is disposed in the central portion of the reset magnetic circuit.
 3. An electromagnetic actuator mechanism, as claimed in claim 1, in which said opposing flux means comprises a winding linking said armature. 